1. Field of the Invention
The present invention relates to a claw-pole permanent-magnet stepping motor. More particularly, the present invention relates to a claw-pole permanent-magnet stepping motor that minimizes external flux leakage, minimizes magnetic circuit obstructions common in low profile designs, and reduces costs.
2. Description of the Related Art
A claw-pole permanent-magnet stepping motor is a type of hybrid stepping motor. Magnetic parts known as claw poles, form a phase A inductor and a phase B inductor in the claw-pole permanent-magnet stepping motor. Claw poles are widely used in commercial devices since they can be produced inexpensively and accurately with plate-pressing technology.
Referring now to FIG. 5, a conventional claw-pole permanent-magnet stepping motor 100 includes a permanent magnet 103 secured to a rotor 102. Permanent magnet 103 is constructed and magnetized to form multiple radial poles, as shown.
Rotor 102 is rotationally supported by a bottom bearing, not shown, and secured to a case unit 113. Rotor 102, is supported at a top by a bearing 115 secured to a securing member 114 on a case unit 112. Case units 112113 are formed from a magnetic material.
Case units 112, 113 respectively house a phase A inductor and a phase B inductor arranged symmetrically about rotor 102. The phase A inductor and the phase B inductor are formed from separate claw poles 104, 105, 106, 107. A coil 108 wraps around claw poles 104 and 105. A coil 109 wraps around claw poles 106 and 107
A diameter L1 is defined on the arcuate section of case units 112, 113. A total case unit length L2 is defined along rotor 102. Diameter L1 and length L2 are designed to form roughly a 2:1 ratio, as shown.
During operation, power is alternately applied to the phase A inductor and the phase B inductor. As a result, magnetic attraction, based on the arrangement of teeth, takes place between permanent magnet 103 and claw poles 104, 105, 106, 107. The magnetic attraction drives a stepping operation that provides rotational torque.
It should be understood that claw-pole permanent-magnet stepping motor 100 cannot be used in devices that impose restrictions on outer diameter L1 of case units 112, 113.
Additionally, devices employing claw-pole permanent-magnet stepping motor 100 must provide a wide attachment area since motor 100 is secured to the device using bolts and nuts via a set of securing holes 114a, 114a formed on securing member 114 of case unit 112.
It is an object of the present invention to provide a claw-pole permanent-magnet stepping motor that overcomes the issues described above.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor that may be attached or internally disposed in devices that impose outer dimension restrictions on a case unit.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor that eliminates magnetic circuit obstructions that accompany low-profile designs.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor that limits external flux leakage.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor that employs a case unit that can be produced simply and with high precision.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor that includes a case unit formed with a lateral cross-section shaped roughly as an oval shape with flat sides, flat side walls, and continuously formed thick arcuate sections.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor where a total length of a case unit along the longitudinal axis of the rotor to a diameter of arcuate sections of a pair of case units is a ratio of at least 1:1 and preferably a ratio of 2:1.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor where a permanent magnet faces a phase A inductor and a phase B inductor to provide adequate rotational torque during operation.
Briefly stated, the present invention relates to a claw-pole permanent-magnet stepping motor that includes a pair of cases containing two or more inductors in symmetrical arrangement with multiple claw poles. The case unit has an oval shape having thin flat side walls or thin stepped side walls and connecting thick arcuate surfaces operating to resist external flux leakage from the motor and eliminating magnetic circuit obstructions. The cases, side walls, and inductors allow the motor to have a width to length ratio from about one to one to about one to two thus allowing a reduction in size and a low profile design while retaining output torque.
According to an embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, comprising: a first and a second case unit having a total length, a rotor having at least a first and a second permanent magnet, the first and the second case units having a shape supporting the rotor, a third and a fourth arcuate section on each the first and the second case units, a fifth and a sixth side wall section joining each respective the third and forth arcuate sections in a continuous flattened-oval shape about the rotor, the third and the forth arcuate sections each having a first diameter, and a ratio of the total length to the first diameter is at least 1:1, whereby the claw-pole permanent magnet stepping motor has a reduced size, eliminates magnetic circuit obstructions, and prevents external flux leakage to allow use with magnetic devices while providing an adequate rotational torque.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, wherein: the ratio is preferably 2:1 whereby the claw-pole permanent magnet stepping motor has a reduced size while providing adequate rotational torque despite the ratio.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, wherein: the third and the fourth arcuate sections each have a first thickness, the fifth and the sixth wall sections each have a second thickness, and the first thickness being greater than the second thickness, whereby size is reduced, magnetic circuit obstructions are eliminated, and external flux leakage is minimized.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, wherein: the fifth and the sixth sections each having a planar shape and being closer to the rotor than the third and the fourth arcuate sections, and the at least first case unit having a flattened-oval cross section, whereby the claw-pole permanent magnet stepping motor has a reduced size.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, further comprising: a first thin wall section on each the fifth and the sixth sections orthogonal each the third and the fourth arcuate sections, the first thin wall section having a third thickness, and the third thickness being less than the second thickness, whereby the claw-pole permanent magnet stepping motor may be made with an increased torque while retaining a same external size.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, further comprising: a first metal bearing in the first case unit, a second metal bearing in the second case unit, the rotor supported between the first and the second metal bearings, a plurality of poles on the first and second permanent magnets, a first and a second phase inductor in each respective the first and the second unit case opposite each respective the first and second permanent magnet, the first and the second phase inductors disposed symmetrically in each respective the first and the case units, and the first and the second phase inductors each formed from at least a first and a second magnetic plate each including multiple claw-poles and a first and a second coil each with a set of connectors, whereby the adequate rotational torque is created.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, comprising: a first and a second case unit having a total length, the first and the second case units including a magnetic material, a rotor having at least a first and a second permanent magnet, the first and the second case units having a shape supporting the rotor, a third and a fourth arcuate section on each the first and the second case units, a fifth and a sixth side wall section joining each respective the third and forth arcuate sections in a continuous flattened-oval shape about the rotor, the third and the forth arcuate sections each having a first diameter, a ratio of the total length to the first diameter is preferably 2:1, the third and the fourth arcuate sections each have a first thickness, the fifth and the sixth wall sections each have a second thickness, the first thickness being greater than the second thickness, the fifth and the sixth sections each having a planar shape and being closer to the rotor than the third and the fourth arcuate sections, the at least first case unit having a flattened-oval cross section, whereby the claw-pole permanent magnet stepping motor has a reduced size, eliminates magnetic circuit obstructions, and prevents external flux leakage to allow use with magnetic devices while providing an adequate rotational torque, a first metal bearing in the first case unit, a second metal bearing in the second case unit, the rotor supported between the first and the second metal bearings, a plurality of poles on the first and second permanent magnets, a first and a second phase inductor in each respective the first and the second unit case opposite each respective the first and second permanent magnet, the first and the second phase inductors disposed symmetrically in each respective the first and the case units, and the first and the second phase inductors each formed from at least a first and a second magnetic plate each having multiple claw-poles and a first and a second coil each with a set of connectors, whereby the adequate rotational torque is created.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, comprising: a first and a second case unit, the first case unit and the second case unit having a first total length, a rotor including a first and a second permanent magnet, the first and the second case units including a magnetic material, the first and the second case units having a shape supporting the rotor, a permanent magnet magnetized to form a plurality of poles, the permanent magnet on the roter, a first phase inductor, a second phase inductor, the first and the second phase inductors disposed symmetrically in each respective the case unit, the first and the second phase inductors each including at least a plurality of claw poles and a coil, the first and the second case units having a first diameter, and a ratio of the first total length to the first diameter is at least 1:1, whereby the claw-pole permanent magnet stepping motor has a reduced size, eliminates magnetic circuit obstructions, and prevents external flux leakage to allow use with magnetic devices while providing an adequate rotational torque.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, wherein: the ratio is preferable 2:1, whereby the adequate rotational torque is maintained.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, further comprising: a securing section detachably attached to an outside side surface of at least one of the first and the second case unit, a securing section containing an externally threaded section, and the securing section being detatachably fixable to an external attachment base for the claw-pole permanent magnet stepping motor, whereby the claw-pole permanent magnet stepping motor may be easily affixed to an external device.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, wherein: each of the first and the second phase inductors includes the coil and a magnetic plate formed integrally from a magnetic material, each the magnetic plate having a shape, including a flat oval-shaped section and an extending plurality of claw-poles, for sliding insertion in each respective the first and the second case unit, whereby assembly time is reduced and efficiency increased.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, wherein: each coil includes a coil bobbin, an insulated copper wire wrapped around the coil bobbin, and a connector, the coil bobbin including a first and a second collar, the connector disposed at at least one of the first and the second collar orthogonal to the coil, and the coil bobbin having a flat oval shape with arcuate sections, whereby the coils are quickly install-able inside each respective the first and the second case units.